The use of hormone replacement therapy for bone loss prevention in post-menopausal women is well precedented. The normal protocol calls for estrogen supplementation using such formulations containing estrone, estriol, ethynyl estradiol, 17β-estradiol, esterified estrogens, or conjugated estrogens isolated from natural sources (i.e. Premarin® conjugated estrogens from Wyeth-Ayerst) or synthetic estrogens. In some patients, therapy may be contraindicated due to the proliferative effects of unopposed estrogens (estrogens not given in combination with progestins) have on uterine tissue. This proliferation is associated with increased risk for endometriosis and/or endometrial cancer. The effects of unopposed estrogens on breast tissue are less clear, but are of some concern. The need for estrogens which can maintain the bone sparing effect while minimizing the proliferative effects in the uterus and breast is evident. Certain nonsteroidal antiestrogens have been shown to maintain bone mass in the ovariectomized rat model as well as in human clinical trials. Tamoxifen (sold as Novadex® brand tamoxifen citrate by Zeneca Pharmaceuticals, Wilmington, Del.), for example, is a useful palliative for the treatment of breast cancer and has been demonstrated to exert an estrogen agonist-like effect on the bone, in humans. However, it is also a partial agonist in the uterus and this is cause for some concern. Raloxifene, a benzothiophene antiestrogen, has been shown to stimulate uterine growth in the ovariectomized rat to a lesser extent than Tamoxifen while maintaining the ability to spare bone. A suitable review of tissue selective estrogens is seen in the article “Tissue-Selective Actions Of Estrogen Analogs”, Bone Vol. 17, No. 4, October 1995, 181S-190S.
The use of indoles as estrogen antagonists has been reported by Von Angerer, Chemical Abstracts, Vol. 99, No. 7 (1983), Abstract No. 53886u. Also, see, J. Med. Chem. 1990, 33, 2635-2640; J. Med. Chem. 1987, 30, 131-136. Also see Ger. Offen., DE 3821148 A1 891228 and WO 96/03375. These prior art compounds share structural similarities with the present compounds, but are functionally different. For compounds containing a basic amine, there is no phenyl group to rigidify the side chain.
WO A 95 17383 (Karo Bio AB) describes indole antiestrogens with long straight chains. Another related patent WO A 93 10741 describes 5-Hydroxyindoles with a broad range of side chains. WO 93/23374 (Otsuka Pharmaceuticals, Japan) describes compounds sharing structural similarities with those of the present invention, except with the structure referred to as R3 in the present formulas I and II, below, is defined as thioalkyl and the reference discloses no such compounds having chains from the indole nitrogen having the same structure as the ones provided by the present invention.
In their article Postmenopausal Hormone replacement therapy with estrogen periodically supplemented with antiestrogen, Am. J. Obstet. Gynecol., Vol. 140, No. 7, 1981, pp. 787-792, Kauppila et al. describe their study of postmenopausal estrogen therapy of seven-week estrogen regimens followed by 10-day treatments with the antiestrogen clomiphene citrate.
Also, in their article Comparison of Megestrol Acetate and Clomiphene Citrate as Supplemental Medication in Posmenopausal Oestrogen Replacement Therapy, Arch. Gynecol. (1983) 234:49-58, Kauppila et al. describe combination therapies in postmenopausal women of estrogen with random supplementation of megestrol acetate or clomiphene citrate.
U.S. Pat. No. 4,894,373 (Young) teaches the use of antiestrogens, including clomiphene and its isomers, citrates and derivatives, in the absence of estrogen for treating menopausal symptoms and treating or preventing osteoporosis. U.S. Pat. No. 5,552,401 (Cullinan et al.) describes benzothiophene compounds as useful for the treatment of various medical indications associated with post-menopausal syndrome, and uterine fibroid disease, endometriosis, and aortal smooth muscle cell proliferation, the compounds being used in pharmaceutical formulations optionally containing estrogen or progestin. U.S. Pat. Nos. 5,646,137 and 5,591,753 (both issued to Black et al.) discloses methods of treating osteoporosis with formulations of raloxefine-type arylbenzothiophene compounds in conjunction with a progestin selected from medroxyprogesterone, norethindrone or norethynodrel, or pharmaceutically acceptable salts thereof. U.S. Pat. No. 5,550,107 (Labrie) claims an invention comprising the treatment of breast or endometrial cancer with an antiestrogen together with at least one compound selected from the group of an androgen, a progestin, at least one inhibitor of sex steroid formation, especially 17β-hydroxysteroid dehydrogenase and aromatase activity, at least one inhibitor of prolactin secretion, one inhibitor of growth hormone secretion and one inhibitor of ACTH secretion. U.S. Pat. No. 5,672,609 (Bryant et al.) discloses pyridine compounds useful in treating post menopausal syndrome and formulations therefore containing estrogen or progestin. U.S. Pat. No. 5,534,527 (Black et al.) teaches the use of aroylbenzothiophenes and estrogens in the inhibition of bone loss.